Extended treatment zone catheter

ABSTRACT

A catheter having an extended treatment zone for cooling tissue is provided. The catheter includes an elongate catheter body having a distal tip, and a fluid injection conduit disposed inside the catheter body defining a return lumen therein. The fluid injection conduit further defines two or more injection orifices including a first distal orifice near the distal tip, and a second orifice longitudinally offset along the fluid injection conduit to be less proximate the distal tip than the first orifice. Fluid cryogen flowing through the orifices creates an extended tissue cooling contour about the distal end portion of the catheter. At least one ECG ring electrode is provided about the catheter body near the second orifice. The catheter may thus provide for electrocardiographic mapping of tissue nodes lying transversely between the distal tip and the ECG ring electrode.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part of U.S. patent application Ser. No. 10/338,274, filed Jan. 08, 2003, entitled COOLANT INJECTION, which is a continuation of U.S. patent application Ser. No. 09/850,668, filed May 07, 2001, now issued Pat. No. 6,540,740, entitled CRYOSURGICAL CATHETER, which is a continuation of U.S. patent application Ser. No. 09/201,071, filed Nov. 30, 1998, now issued Pat. No. 6,235,019, entitled CRYOSURGICAL CATHETER, which is a continuation of U.S. patent application Ser. No. 08/893,825, filed Jul. 11, 1997, now issued Pat. No. 5,899,899, entitled CRYOSURGICAL LINEAR ABLATION STRUCTURE, which is a continuation-in-part of U.S. patent application Ser. No. 08/807,382, filed Feb. 27, 1997, now issued Pat. No. 5,899,898, and entitled CRYOSURGICAL LINEAR ABLATION, all of which are incorporated herein by reference.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

n/a

FIELD OF THE INVENTION

The invention relates to catheters, and more particularly to cryosurgical catheters used for tissue ablation.

BACKGROUND OF THE INVENTION

Many medical procedures are performed using minimally invasive surgical techniques, wherein one or more slender implements are inserted through one or more small incisions into a patient's body. With respect to ablation, the surgical implement can include a rigid or flexible structure having an ablation device at or near its distal end that is placed adjacent to the tissue to be ablated. Radio frequency energy, microwave energy, laser energy, extreme heat, and extreme cold can be provided by the ablation device to kill the tissue.

With respect to cardiac procedures, a cardiac arrhythmia can be treated through selective ablation of cardiac tissue to eliminate the source of the arrhythmia. A popular minimally invasive procedure, radio frequency (RF) catheter ablation, includes a preliminary step of conventional electrocardiographic mapping followed by the creation of one or more ablated regions (lesions) in the cardiac tissue using RF energy. Multiple lesions are frequently required because the effectiveness of each of the proposed lesion sites cannot be predetermined due to limitations of conventional electrocardiographic mapping. Often, five lesions, and sometimes as many as twenty lesions may be required before a successful result is attained. Usually only one of the lesions is actually effective; the other lesions result in unnecessarily destroyed cardiac tissue.

Deficiencies of radio frequency ablation devices and techniques have been overcome by using cold to do zero degree or ice mapping prior to creating lesions, as taught in U.S. Pat. Nos. 5,423,807; and 5,281,213; and 5,281,215. However, even though combined cryogenic mapping and ablation devices permit greater certainty and less tissue damage than RF devices and techniques, both the cryogenic and the RF devices are configured for spot or roughly circular tissue ablation.

Spot tissue ablation is acceptable for certain procedures. However, other procedures can be more therapeutically effective if multiple spot lesions along a predetermined line, or a single elongate or linear lesion is created in a single ablative step. Radio frequency ablation devices are known to be able to create linear lesions by dragging the ablation tip along a line while it is active. However, no cryogenic devices are known that are optimized for, or which are even minimally capable of, creating an elongate lesion.

Furthermore, when using a catheter to simultaneously perform electrocardiographic mapping as well as to treat tissue being mapped, the treatment zone extending around the catheter is limited. This is especially problematic with regard to bipolar or multipolar electrode catheters having multiple electrocardiogram (ECG) leads disposed at the distal tip. The arrangement of the ECG leads around the distal tip in relation to the tissue treatment element is such that once a tissue node of interest has been mapped, the catheter's treatment zone extending around the distal tip is generally not large enough or shaped to encompass the tissue node. The catheter must be moved of repositioned to effectuate treatment. It would be desirable therefore, to provide a catheter having the electrocardiographic mapping capabilities as discussed above in addition to an extended treatment zone to as to better perform the twin functions of mapping and treatment or ablation of tissue.

SUMMARY OF THE INVENTION

The present invention provides a cryogenic catheter having an elongate outer member and a plurality of inner members disposed within the elongate outer member. The inner members have a plurality of controllable openings formed thereon for the selective release of cryogenic fluid. A plurality of electrode members is disposed on an external surface of the outer member. The inner members may be positioned in a staggered configuration or alternatively at least one inner member may be disposed within another inner member. In such a configuration, one of the inner members may be slidable or rotatable to the other.

DESCRIPTION OF THE DRAWINGS

A more complete understanding of the present invention, and the attendant advantages and features thereof, will be more readily understood by reference to the following detailed description when considered in conjunction with the accompanying drawings wherein:

FIG. 1 is a schematic illustration of an embodiment of a cryosurgical system in accordance with the invention;

FIG. 2 is a schematic depiction of the chambers of the heart showing placement of the catheter of FIG. 1;

FIG. 3 illustrates the tip region of one embodiment of the catheter in accordance with the invention;

FIG. 4 illustrates an alternative embodiment of the catheter of FIG. 3;

FIG. 5 illustrates yet another embodiment of the catheter;

FIG. 6 illustrates a deformable tip for a catheter;

FIG. 7 illustrates yet another embodiment of the catheter;

FIG. 8 is a sectional view of the catheter of FIG. 7 taken along line 8-8;

FIG. 9 is a sectional view of an alternative embodiment of the linear ablation catheter illustrated in FIG. 7;

FIG. 10 illustrates an expansion chamber within a portion of a helical coil;

FIG. 11 illustrates a portion of a catheter having an elongate, thermally-transmissive strip;

FIG. 12 is a sectional view of the catheter of FIG. 3 taken along line 12-12;

FIG. 13 is a sectional view of the catheter of FIG. 3 taken along line 13-13;

FIGS. 14-16 are sectional views of additional catheter embodiments;

FIG. 17 illustrates an inner face of a flexible catheter member;

FIG. 18 depicts yet another embodiment of a catheter in accordance with the invention;

FIG. 19 is a table illustrating cooling performance of a catheter in accordance with the invention;

FIG. 20 is a sectional view of another catheter embodiment;

FIG. 21 is a sectional view of a portion of the catheter of FIG. 20;

FIG. 22 is a detailed view of an area of the catheter portion illustrated in FIG. 21;

FIG. 23 is an illustration of yet another catheter embodiment;

FIG. 24 depicts still another catheter embodiment;

FIG. 25 illustrates yet another embodiment of the catheter;

FIG. 26 is a sectional view of the catheter of FIG. 25 taken along line 26-26;

FIG. 27 illustrates yet still another embodiment of the catheter;

FIG. 28 illustrates the catheter of FIG. 27 in a second configuration;

FIG. 29 is a sectional view of the catheter of FIG. 28 taken along line 29-29;

FIG. 30 is a sectional view of the catheter of FIG. 28 taken along line 30-30;

FIG. 31 illustrates yet another embodiment of the catheter;

FIG. 32 illustrates the catheter of FIG. 31 in a second configuration;

FIG. 33 is a sectional view of the catheter of FIG. 32 taken along line 33-33;

FIG. 34 is a sectional view of the catheter of FIG. 32 taken along line 34-34;

FIG. 35 illustrates yet another embodiment of the catheter;

FIG. 36 is a sectional view of yet another embodiment of the catheter;

FIG. 37 is a sectional view of the catheter of FIG. 36 after rotation;

FIG. 38 illustrates yet another embodiment of the catheter;

FIG. 39 illustrates the catheter of FIG. 38 in a second configuration;

FIG. 40 illustrates one embodiment of the catheter proximate a treatment node, with a limited treatment zone shown around the catheter;

FIG. 41 illustrates another embodiment of the catheter proximate the treatment node of FIG. 40, with an extended treatment zone provided by the catheter;

FIG. 42 illustrates an expanded cross-sectional view of the catheter of FIG. 41, taken along lines A-A in FIG. 41;

FIGS. 43A and 43B are perspective views of two addition embodiments of the flow conduit of the catheter of FIG. 42; and

FIG. 44 illustrates a cross-sectional view of yet another embodiment of the catheter

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a schematic illustration of a cryosurgical system in accordance with the invention. The system includes a supply of cryogenic or cooling fluid 10 in communication with the proximal end 12 of a flexible catheter 14. A fluid controller 16 is interposed or in-line between the cryogenic fluid supply 10 and the catheter 14 for regulating the flow of cryogenic fluid into the catheter in response to a controller command. Controller commands can include programmed instructions, sensor signals, and manual user input. For example, the fluid controller 16 can be programmed or configured to increase and decrease the pressure of the fluid by predetermined pressure increments over predetermined time intervals. In another exemplary embodiment, the fluid controller 16 can be responsive to input from a foot pedal 18 to permit flow of the cryogenic fluid into the catheter 14. One or more temperature sensors 20 in electrical communication with the controller 16 can be provided to regulate or terminate the flow of cryogenic fluid into the catheter 14 when a predetermined temperature at a selected point or points on or within the catheter is/are obtained. For example a temperature sensor can be placed at a point proximate the distal end 22 of the catheter and other temperature sensors 20 can be placed at spaced intervals between the distal end of the catheter and another point that is between the distal end and the proximal end.

The cryogenic fluid can be in a liquid or a gas state. An extremely low temperature can be achieved within the catheter, and more particularly on the surface of the catheter by cooling the fluid to a predetermined temperature prior to its introduction into the catheter, by allowing a liquid state cryogenic fluid to boil or vaporize, or by allowing a gas state cryogenic fluid to expand. Exemplary liquids include chlorodifluoromethane, polydimethylsiloxane, ethyl alcohol, HFC's such as AZ-20 (a 50-50 mixture of difluoromethane & pentafluoroethane sold by Allied Signal), and CFC's such as DuPont's FREON. Exemplary gasses include nitrous oxide, and carbon dioxide.

The catheter 14 includes a flexible member 24 having a thermally-transmissive region 26 and a fluid path through the flexible member to the thermally-transmissive region. A fluid path is also provided from the thermally-transmissive region to a point external to the catheter, such as the proximal end 12. Although described in greater detail below, exemplary fluid paths can be one or more channels defined by the flexible member 24, and/or by one or more additional flexible members that are internal to the first flexible member 24. Also, even though many materials and structures can be thermally conductive or thermally transmissive if chilled to a very low temperature and/or cold soaked, as used herein, a “thermally-transmissive region” is intended to broadly encompass any structure or region of the catheter 14 that readily conducts heat.

For example, a metal structure exposed (directly or indirectly) to the cryogenic fluid path is considered a thermally-transmissive region 26 even if an adjacent polymeric or latex catheter portion also permits heat transfer, but to a much lesser extent than the metal. Thus, the thermally-transmissive region 26 can be viewed as a relative term to compare the heat transfer characteristics of different catheter regions or structures.

Furthermore, while the thermally-transmissive region 26 can include a single, continuous, and uninterrupted surface or structure, it can also include multiple, discrete, thermally-transmissive structures that collectively define a thermally-transmissive region that is elongate or linear. Depending on the ability of the cryogenic system, or portions thereof, to handle given thermal loads, the ablation of an elongate tissue path can be performed in a single or multiple cycle process without having to relocate the catheter one or more times or drag it across tissue. Additional details of the thermally-transmissive region 26 and the thermal transfer process are described in greater detail below.

In exemplary embodiments of the invention, the thermally-transmissive region 26 of the catheter 14 is deformable. An exemplary deformation is from a linear configuration to an arcuate configuration and is accomplished using mechanical and/or electrical devices known to those skilled in the art. For example, a wall portion of the flexible member 24 can include a metal braid to make the catheter torqueable for overall catheter steering and placement. Additionally, a cord, wire or cable can be incorporated with, or inserted into, the catheter for deformation of the thermally transmissive region 26.

The cryogenic system of FIG. 1 is better understood with reference to its use in an operative procedure as shown in FIG. 2. Following the determination of a proposed lesion site within a heart chamber 28, for example, the catheter 14 is directed through a blood vessel 30 to a region within the heart, such as an atrial or ventricular chamber, where the lesion will be made. The thermally-transmissive region 26 is placed proximate to the tissue to be ablated. The thermally-transmissive region of the catheter may be deformed to conform to the curvature of the tissue before, during, or after placement against the tissue. The controller 16 allows or causes cryogenic fluid to flow from the cryogenic fluid supply 10 to the fluid path in the catheter 14 and thence to the thermally-transmissive region 26 to ablate the desired area or to cold map along the same tissue area. In one embodiment (e.g., FIG. 12) a first conduit is concentric within a second conduit and cooling fluid travels to a thermally-transmissive region proximate a closed distal end of the catheter through a first conduit (fluid path) and is exhausted from the catheter through the second conduit (fluid path).

Having described the function of the cryogenic catheter 14 and its use in a system context, several exemplary embodiments of the thermally-transmissive region 26 of the catheter are now described in greater detail. FIGS. 3, 4, 5, 12-16 and 18 illustrate embodiments of the catheter, or portions thereof, having two or more thermally-transmissive segments in a spaced-apart relationship. Each of the illustrated catheters includes a closed tip 32 that can include a thermally-transmissive material.

Referring specifically to the embodiment depicted in FIG. 3, multiple thermally-transmissive elements 34 are integral with a distal portion of a catheter. Each of the thermally-transmissive elements 34 includes a first side or face 36 (shown in FIGS. 12 and 13) exposed to a cryogenic fluid path and cryogenic fluid (shown by arrows) and a second side or face 38 exposed to points exterior to the catheter. As shown in FIG. 13, the first side 36 and/or second side 38 of any or all of the thermally-transmissive elements 34 can be substantially flush with, recessed below, or protruding from the inner surface 40 and outer surface 42 of a portion of the catheter. The thermally-transmissive elements 34 are separated by flexible portions of material 44 than can range from slightly less thermally-transmissive than the adjacent thermally-transmissive elements to substantially less thermally-transmissive than the adjacent elements. In the illustrated embodiment of FIG. 3, the thermally-transmissive elements 34 are annular, cylindrical elements which are made of gold-plated copper, bronze, or stainless steel. Thermocouples 35 can be associated with one or more of the elements 34 and the tip 32. The thermally-transmissive elements 34 can be completely exposed, embedded, or a combination thereof along the full 360.degree. of the catheter's circumference. In certain applications the thermally-transmissive elements traverse or define less than 360.degree. of the catheter's circumference as shown in FIGS. 14-16 and as described below. The longitudinal width of each thermally-transmissive element 34, the spacing between elements, the material thickness, and the material composition are matched with a selected cryogenic fluid, one or more cryogenic fluid delivery locations within the catheter and fluid delivery pressure to produce overlapping cold regions which produce a linear lesion.

The embodiment illustrated in FIG. 4 is substantially identical to the embodiment of FIG. 3, however, at least one of the thermally-transmissive elements 34 includes a first open end 46 that defines a first plane and a second open end 48 that defines a second plane, wherein the first and second planes intersect to give the annular elements a wedge-like appearance. Such a configuration permits adjacent thermally-transmissive elements 34 to be positioned very closely together, but it can limit the possibilities for deforming the thermally-transmissive region 26, which, in this embodiment, is flexible in the direction indicated by the arrow.

With respect to the embodiments shown in both FIGS. 3 and 4, the thermally-transmissive elements 34 are substantially rigid and are separated and/or joined by a flexible material 44. However, in other embodiments the thermally-transmissive elements 34 are flexible and are interdigitated with either rigid or flexible segments. FIG. 5, for example, illustrates an embodiment of the cryogenic catheter having three thermally-transmissive elements 34 that are flexible. The flexibility is provided by a folded or bellows-like structure 50. In addition to being shapable, a metal bellows can have enough stiffness to retain a selected shape after a deforming or bending step.

Instead of, or in addition to, flexible, thermally-transmissive elements 34 and/or flexible material 44 between elements, the distal tip 32 (or a portion thereof) can be deformable. For example, FIG. 6 illustrates a tip 32 having thermally-transmissive, flexible, bellows 50.

Referring now to FIGS. 7-10, a different approach is shown for providing multiple thermally-transmissive segments in a spaced-apart relationship. FIG. 7 illustrates a catheter embodiment having an elongate, thermally-transmissive region 26 that includes a helical coil 52 at least partially embedded in the flexible member 24. As shown in FIG. 8, at least a first portion 54 of the helical coil 52 is exposed to a fluid path within the flexible member 24 and a second portion 56 of the helical coil is exposed to the exterior of the flexible member. As described above with respect to FIG. 13, the first portion 54 of the coil can be substantially flush with, recessed below, or protruding from an inner surface 58 of the flexible member 24. Similarly, the second portion 56 of the coil 52 can be substantially flush with, recessed below, or protruding from an outer surface 60 of the flexible member 24.

In the embodiment of FIG. 8, the second portion 56 of the coil 52 is exposed along only a portion of the outer circumference of the flexible member 24 to define a longitudinally-elongate, thermally-transmissive region 26. This configuration can be provided by eccentrically mating the helical coil 52 to the catheter so that the longitudinal axis of the coil and the longitudinal axis of the catheter are substantially parallel. The eccentric positioning of the coil 52 provides excellent cooling performance because the surface area available for thermal exchange between the first portion 54 of coil and the cryogenic fluid is greater than the surface area available for thermal exchange between the second portion 56 of the coil and adjacent tissue where cooling power is delivered by each exposed coil portion to provide a linear lesion.

Referring now to FIG. 9, an alternative embodiment is shown wherein a first portion 62 of the coil 52 is exposed around the entire circumference of the flexible member 24, and a second portion 64 is exposed to a fluid path around the inner surface of the flexible member 24. This is achieved by having the longitudinal axis of the helical coil 52 co-axial with the longitudinal axis of the catheter.

In the embodiments illustrated in FIGS. 7-9, the coil 52 is solid. However, in other embodiments the coil can be an elongate, hollow, gas expansion chamber. For example, FIG. 10 illustrates a portion of a helical coil 52 that includes a passage that defines at least a portion of a fluid path through a flexible member of the catheter. The coil 52 defines a first fluid path diameter at a fluid entry point 66 and a second fluid path diameter that is greater than the first fluid path diameter at a gas expansion or boiling location 68. Gas escaping from a fluid exit point 70 can be exhausted through an open central region of the coil and/or another passage through the flexible member 24.

FIG. 11 illustrates an embodiment of the catheter wherein a continuous, elongate, thermally-transmissive strip 72 is longitudinally integrated with a flexible member 24. The strip can include a bellows-like structure. As described above with respect to other embodiments, a first portion of the strip can be substantially flush with, recessed below, or protrude from the outer surface of the flexible member. Similarly, a second portion of the strip can be substantially flush with, recessed below, or protrude from an inner surface of the flexible member.

Referring now to FIG. 12, an embodiment of the catheter is illustrated having a second or inner flexible member 74 within a lumen of first or outer flexible member 24, wherein the second flexible member defines a fluid path to the thermally-transmissive region 26. The inner member 74 can include a single opening 76 at or near the tip 32. Cryogenic fluid is expelled from the opening 76 and returns to the proximal end of the catheter along a fluid path defined by the outer wall of the inner member 74 and the inner wall of the outer member 24. This fluid path configuration is also partially illustrated in FIGS. 8, 9, and 13. Alternatively, as also shown in FIG. 12, the inner member 74 can be provided with multiple openings 78 proximate to and/or aligned with the inner face of one or more thermally-transmissive elements 34 to achieve more uniform cooling across the entire elongate, thermally-transmissive region 26.

Referring now to FIGS. 14-16, sectional views of catheter embodiments are illustrated to show alternative configurations for thermally-transmissive elements. The previously described thermally-transmissive elements 34 are arcuate and form complete and continuous 360 degree structures that traverse the complete circumference of the catheter, notwithstanding being flush with, depressed below, or raised above the outermost surface of the flexible member 24. However, the arcuate elements 34′, 34″, and 34′″ illustrated in FIGS. 14-16, respectively, traverse less than 360 degrees of the circumference of the first flexible member and do not form complete loops. For example, in FIG. 14, element 34′ defines an approximately 270 degree arc. In FIG. 15 the thermally-transmissive element 34″ defines an approximately 180 degree arc; and in FIG. 16, the thermally-transmissive element 34″′ defines an approximately 90 degree arc. A catheter can include combinations of element types, such as a complete ring or loop element, a 270 degree element and a 180 degree element as desired to define a thermally transmissive region. In addition to the having applicability with respect to rigid thermally-transmissive elements, the bellows-like elements can also be less than 360 degrees.

The less than 360 degree arcuate elements provide unique functional benefits with respect to thermal transfer and flexibility of the thermally-transmissive region. For example, because the portion of the catheter between the opposing ends of element 34′, 34″, 34′″ does not include a rigid structure, but rather only the resilient material of flexible member 24, the thermally-transmissive region of the catheter can be more tightly curved (gap between ends inward and element facing outward) than it could with complete 360 degree structures, especially if the elements are relatively long longitudinally.

The inner member 74 can be adapted to direct cooling fluid at only the thermally transmissive element(s) and the shape and/or the number of openings for cooling fluid can be configured differently depending on the length of the arc defined by the thermally-transmissive element(s). For example, FIG. 14 illustrates an embodiment of the inner member having three openings opposing the thermally transmissive element 34′; FIG. 15 illustrates two openings for a smaller arc; and FIG. 16 discloses a single opening for an even smaller arc.

Another advantage to providing one or more thermally-transmissive elements that have a less than 360 degree configuration is that limiting the span of the elements to a desired lesion width, or somewhat greater than a desired lesion width, reduces the thermal load on the system and/or permits colder temperatures to be achieved than with respect to a complete 360 degree structure. Unnecessary and perhaps undesirable cooling does not occur at any other location along the catheter except at an elongate region of predetermined width. A similar effect can also be achieved by providing a non-circular 360 degree element or by eccentrically mounting a circular 360 degree element with respect to the flexible member, wherein a portion of the 360 degree element is embedded within the wall of the flexible member or otherwise insulated from the cryogenic fluid path in a manner similar to that shown in FIG. 8.

Referring now to FIG. 17, a portion of the inner face of an outer flexible member showing in an exemplary embodiment, thermal transfer pins 80 protruding from the inner face of a thermally-transmissive element 34. The pins permit thermal transfer through the flexible member 24. As with the other features of the invention, the pins are equally suitable for complete 360 degree element structures or less than 360 degree structures. Although only pins are shown on any geometric or surface means to increase heat transfer including but not limited to pins, irregularities, channels or surface modifications may be used. Referring now to FIG. 18, yet another embodiment of the catheter is shown wherein rigid metal rings 34 a-c are interdigitated with flexible segments 44 a-c to define a first flexible member and a thermally-transmissive region approximately one inch in length. A second flexible member is concentric within the first flexible member and has an outlet for cryogenic fluid at its distal end. Thermocouples 82 a-c can be associated with one or more of the rings 34 a-c.

It has been described above how the thermal loading of a cooling system can be reduced by providing thermally-transmissive elements that span less than 360 degrees. However, the thermal loading can also be reduced by sequentially cooling the thermally-transmissive region. One way to sequentially cool is to modulate the pressure of the cooling fluid along the fluid path through the flexible member. This modulation can be performed by the fluid controller which can be programmed to increase and decrease the pressure of the fluid by predetermined pressure increments over predetermined time intervals. When the cryogenic fluid is a liquid that provides cooling by changing phase from liquid to gas, the change of pressure alters the physical location along the fluid path where the phase change takes place and concomitantly changes the point of coldest temperature along the thermally-transmissive region. Thus, varying the pressure of the fluid can provide a moving ice-formation “front” along the catheter, enabling the creation of a linear lesion.

Therefore, a method of forming an elongate tissue lesion can include the following steps using any of the above described catheters having an elongate, thermally-transmissive region. In a first step a cryogenic fluid is introduced into the flexible member at a first predetermined pressure. Next, the pressure of the cryogenic fluid is incrementally increased within the flexible member until a second predetermined pressure is achieved. Similarly, the pressure of the cryogenic fluid within the flexible member can be decreased incrementally from the second predetermined pressure to the first predetermined pressure, wherein the steps of incrementally increasing and decreasing the pressure define a thermal cycle. Typically, from one to eight thermal cycles are required to achieve a desired therapeutic effect. In an exemplary method, about ten increments of about five seconds in duration are selected and pressure is increased by about 20 to 40 pounds per square inch in each increment. Thus, using this method an elongate lesion can be created in less than 20 minutes.

FIG. 19 is a table that illustrates sequential cooling in a catheter as described above having a thermally-transmissive region that includes a tip and three elements or rings. The table illustrates three tests conducted in a still bath at 37.degree. C., using AZ-20 as the cryogenic fluid. Alternatively, nitrous oxide could be used as the cryogenic fluid. Associated with each pressure increment are measured temperatures at the tip, first ring, second ring, and third ring. The shaded region illustrates the sequential movement of a target temperature range (upper −40's to low −50's or lower) in response to a change in pressure. Although values are only provided for three rings, a similar effect and pattern is obtained with more than three rings or elements.

Turning now to FIG. 20, a thermally-transmissive portion of another embodiment of a medical device or structure such as a catheter is illustrated in a sectional view. The structure can include an inner passage or lumen as described above with respect to other embodiments, but which is not shown in this illustration for purposes of clarity. Thus, the illustrated portion is the outer passage or lumen that defines an elongate ablation region. Thermally-transmissive elements 84, such as gold plated copper, are joined to adjacent elements by resilient connecting elements 86, such as a stainless steel springs welded to the ends of the elements 84. A resilient bio-compatible material 88 covers the connecting elements 86 and the interstices between adjacent thermally-transmissive elements. In an exemplary embodiment, the material 88 is vulcanized silicone. It should be noted in the illustration that the surface of the elements 84 is contiguous and co-planar with the material 88 to provide a smooth outer surface.

FIG. 21 illustrates a single thermally-transmissive element 84 having reduced diameter ends 90 and 92. The wider central portion 94 provides an expansion chamber for gas (shown by arrows) exiting an apertured inner passage 96. FIG. 22 shows additional detail of the end 90 of the element 84. The end 90 is textured, such as by providing serrations 98, to provide a good adhesion surface for the material 88.

Referring now to FIG. 23, a thermally-transmissive portion of yet another embodiment of a flexible cryogenic structure is illustrated in a sectional view. In this embodiment an inner, apertured structure 100 has a flat wire 102 wrapped around it in a spiral manner. Thermally-transmissive segments 104 are disposed upon the wire 102 in a spaced-apart relationship, and a flexible, bio-compatible material 106 fills the interstices between segments 104. A thermocouple 108 can be associated with each segment 104. A wire 109 connects the thermocouple 108 to instrumentation near the proximal end of the structure. The exterior surface of the structure is smooth, and the structure can include 3 to 12 segments 104. In an exemplary embodiment the inner structure 100 is made of PTFE, the material 106 is 33 D PEBAX, and the wire 102 is stainless steel or Nitinol. An apertured inner passage (similar to that shown in FIG. 21) is placed within the structure.

FIG. 24 illustrates still another embodiment of a cryogenic cooling structure that includes a surface or wall 110 including a polymer or elastomer that is thin enough to permit thermal transfer. For example, polyamide, PET, or PTFE having a thickness of a typical angioplasty balloon or less (below 0.006 inches) provides acceptable thermal transfer. However, the thinness of the wall 110 allows it to readily collapse or otherwise deform under vacuum or near vacuum conditions applied to evacuate fluid/gas from the structure. Accordingly, the structure is provided with one or more supporting elements 112 such as a spring. The cooling structure is illustrated in association with a catheter 114 having a closed distal tip 116 and mono or bipolar ECG rings 118, 120, 122. The thermally-transmissive region is approximately 30 mm in length and is effective for thermal transfer over its entire circumference. However, as illustrated in FIG. 11, the thermally-transmissive region can be confined to specific region(s) of the device's circumference.

Referring now to FIG. 25, an embodiment of the catheter is illustrated having three flexible members or injection tubes 210, 211 and 212 disposed within a first or outer flexible member 200. In an exemplary embodiment, the inner flexible members 210, 211 and 212 are arranged in a staggered configuration within the outer flexible member 200. As used herein, term “staggered” may be used to designate both a linearly/axially staggered configuration or alternatively, a rotationally staggered configuration. The flexible members 210, 211 and 212 thus define multiple staggered fluid paths within the outer member 200. In such a configuration, the injection tubes 210, 211 and 212 allow for greater aggregate cooling power as well as the creation of a variety of different cooling/freeze zones 201, 203 and 205 along the length of the outer flexible member 200. In an exemplary embodiment, thermocouples 204 disposed along the outer surface of the outer flexible member 200 may be integrated with an internal feedback loop to provide independent and variable regulation of these freeze zones.

In an exemplary embodiment, the first inner member 210 includes at least one opening 214 positioned proximate an electrode ring member 207. Cryogenic fluid is expelled from the opening 214 and returns to the proximal end of the catheter along a fluid path defined by the inner wall 218 of the outer member 200, as shown in FIG. 26. Similarly, the second inner member 211 includes at least one opening 215 positioned proximate a second electrode ring member 208. Cryogenic fluid is also expelled from the opening 215 and returns to the proximal end of the catheter along the fluid path defined by the inner wall 218 of the outer member 200. Similarly, the third inner member 212 includes at least one opening 216 positioned proximate a third electrode ring member 209.

Alternatively, the catheter can be provided with only two inner members, or four or more inner members, not shown, disposed within the outer member. The inner members would have one or more openings proximate to and/or aligned with the inner face of one or more transmissive elements, as described earlier herein, to achieve different regions of freeze zones across the entire elongate member. Alternatively, all the staggered inner members may be simultaneously provided with cryogenic fluid to create a linear lesion for selected applications. The flow of cooling fluid along the fluid paths through the flexible members can also be alternated in any number of patterns among the multiple inner members to provide a desired cooling pattern such as a discontinuous or a continuous lesion across the entire catheter.

In an exemplary embodiment, a catheter with a plurality of thermally conductive electrode rings would have an underlying injection tube or tubes controlling the release of cryogenic fluid to each electrode. Such a catheter could be placed in the coronary sinus or endocardially along the atrioventricular junction. Once positioned, an electrogram of interest is located using a specific electrode ring on the catheter. Coldmapping may be performed on the selected location to confirm the correctness of the location. Once, confirmed, the area is cryoablated using the same electrode ring. The same embodiments and others described herein are equally suited to other organs besides the heart and/or any body portion that would benefit from the application of thermal energy.

Referring now to FIG. 27, an embodiment of the catheter is illustrated having an outer member 220 with a fixed injection tube 230 disposed within a slidable sheath or overtube 240 therein. The injection tube and overtube are shown spaced apart for illustrative purposes only. Preferably, the injection tube is sized so that an outer surface of the injection tube engages an inner surface of the overtube while still allowing one member to slide or rotate relative to the other.

The fixed injection tube 230 has multiple openings 232, 234 formed thereon and the slidable overtube also has multiple openings or ports 242, 244 formed thereon. In one configuration shown in FIG. 27, opening 232 on the injection tube 230 coincides or is aligned with opening 242 on the slidable overtube 240. Thus, any fluid exiting the injection tube 230 from opening 232 is able to escape through opening 242.

As the slidable overtube 240 is slid or moved in a first direction as shown by arrow 236 along longitudinal axis 222, opening 232 is covered or blocked by the surface of overtube 240 as now shown in FIG. 28. In a second configuration shown in FIG. 29, opening 234 of injection tube 230 is aligned with opening 244 of overtube 240. In the same configuration, as shown in FIG. 30, opening 242 is not aligned with any opening formed on the surface of injection tube 230. Although only shown in two positions or configurations, the slidable overtube is positionable in any number of positions relative to the fixed injection tube. The overtube may also be used to partially cover the openings on the injection tube to provide for a limited or controlled flow of cryogenic fluid.

Depending on which opening of the injection tube is aligned with the openings formed on the overtube, cryogenic fluid is expelled from the opening and returns to the proximal end of the catheter along a fluid path defined by the inner wall 226 of the outer member 220. The non-aligned opening will not expel fluid since the opening will be blocked. Alternatively, the injection tube and overtube can be provided with three or more openings to achieve multiple cooling/freeze zones along the length of the catheter.

Referring now to FIG. 31, an embodiment of the catheter is illustrated having a slidable injection tube 260 disposed within a fixed sheath or overtube 270. As shown in FIG. 31, both the injection tube 260 and overtube 270 are disposed within a flexible outer member 250. The slidable injection tube 260 has multiple openings 262, 264 formed thereon which allows for the release of cryogenic fluid. The fixed overtube 270 also has multiple perforations or openings 272, 274 formed thereon which allows for the differential release of fluid as described in more detail below. The injection tube may be further provided with a thermistor 254 disposed proximate the distal end of the tube to provide thermistor feedback. In one embodiment, the openings can be controlled by miniaturized means such as micro or nanovalves.

In a first configuration shown in FIG. 3 1, opening 262 of the injection tube 260 coincides or is aligned with opening 274 of the fixed overtube 270. As the slidable injection tube 260 is slid or moved in a first direction as shown by arrow 266, opening 262 is then aligned with corresponding opening 272 on the overtube 270 in FIG. 32.

In this second configuration, as shown in FIGS. 32-34, openings 262, 264 of injection tube 260 are aligned with openings 272, 274 of overtube 270. Although only two configurations for the catheter are shown, the injection tube 260 is positionable in any number of locations relative to the fixed overtube 270.

In operation, cryogenic fluid is expelled from the openings and returns to the proximal end of the catheter along a fluid path defined by an inner wall 256 of the outer member 250. Alternatively, the injection tube 260 and overtube 270 can be provided with multiple openings proximate to and/or aligned with the inner face of one or more thermally-transmissive elements as described earlier herein to achieve more uniform cooling across the entire elongate, thermally-transmissive region.

Referring to FIG. 35, an embodiment of the catheter is illustrated having an outer member 280 with an injection tube 290 with multiple opposed openings 292-297 formed therein. Either the injection tube 290 or the overtube 300 may be slidable in a longitudinal plane to expose and/or cover one or more of the opposed openings on the injection tube 290. For example, as shown in FIG. 35, openings 294, 295 formed on the injection tube 290 are aligned with openings 302, 303 formed on the overtube 230. Furthermore, the injection tube may be positioned in a forwardmost position, not shown, to expose openings on the injection tube proximate the tip of the catheter. In this configuration, the injection tube would provide fluid to cool the area around the tip of the catheter.

In the embodiments described and shown above in FIGS. 32-35, electrode rings as shown in FIG. 25 may be provided along the outer surface of any of the outer members. The electrodes would serve both as electrical conductors and as a thermal transmitter at each location.

Referring to FIGS. 36 and 37, an embodiment of the catheter is illustrated have one or more rotatable members disposed within a flexible outer member 310. In this embodiment, the catheter includes an overtube member 312 and an injection tube member 314, one or both of which are rotatable with respect to one another. In an exemplary embodiment as shown in FIGS. 36 and 37, the injection tube 314 is rotatable relative to the fixed overtube 312. The injection tube 314 may be rotatable in either or both a clockwise and counterclockwise direction as indicated by arrows 320 and 322. As shown in FIG. 36, in a first configuration, opening 316 formed on the overtube 312 aligns with an opening 318 formed on the injection tube 314. As the injection tube 314 is rotated in a counterclockwise direction, the opening 318 on the injection tube 314 is placed out of alignment with the opening 316 formed on overtube 312, as shown in FIG. 37. Alternatively, the injection tube 314 may be fixed in the catheter while the overtube 312 is rotatable. In another embodiment, both the injection tube and overtube may both be rotatable. In yet a further embodiment, the injection tube and/or the overtube are rotatable and slidable within the outer member.

In the embodiments shown and described above, the slidable and rotatable inner and outer tubes may have openings so arranged as to allow the fluid releasing openings to be in a variety of open and closed configurations with a minimum of relational movement between the tubes. For example, as shown in FIG. 38, an outer member 330 has disposed therein one slidably disposed inner tube 336 which has openings 338 formed thereon in a constant sequence, and a matching slidably disposed outer tube 332 which has openings 334 formed thereon in a constant sequence of slightly different length or intervals.

In this configuration, as shown in FIG. 39, small linear relational movements bring the openings on the outer tube 332 and the inner tube 336 into an overlapping configuration.

FIG. 40 illustrates one embodiment of the catheter proximate a treatment node, with a limited treatment zone shown around the catheter. Only the distal end portion of the catheter is shown, labeled generally as 400. The catheter 400 is shown positioned proximate a tissue treatment region or node 401, marked with an “x” in FIG. 40. The treatment node 401 may be, for example, the atrioventricular node or any other discrete locus of tissue to be treated and/or mapped.

Catheter 400 includes a catheter body 402, a distal tip 405 and several ECG leads or rings 410, 415, and 420. Each of the ECG rings is staggered along the length of the catheter body 402 as shown. The ECG rings may be part of a bipolar, tripolar, or quadripolar electrocardiographing mapping apparatus. Each of the ECG rings 410, 415, and 420 are made of an electrically conductive material.

In operation, the catheter is coupled to a source of fluid coolant or cryogen at its proximal end portion (not shown). The coolant is directed to flow in an internal injection lumen or tube (not shown) through to the distal tip portion 405. Generally, the injection tube includes at least one orifice or opening though which the coolant exits the tube and flows into a second return lumen (not shown) back to the proximal end portion of the catheter. The orifice included may be a typical Joule-Thomson gas expansion element, whereupon high pressure coolant in gas phase expands upon exiting the orifice to low pressure, with an attendant drop in temperature. This endothermic process acts to cool the environment immediately around the distal tip 405, which itself may be thermally conductive or heat-transmitting, so as to transmit the cooling generated by the expansion of gases inside the catheter. The cooling process may also be generated by the change in phase of coolant from liquid to gas, in conjunction with Joule-Thomson expansion. This is generally true for coolant that is supplied at mixed gas-liquid phase.

When cooling is thus initiated, the environment around the catheter is cooled to form an iceball, the shape of which is approximately shown by contour 424 in FIG. 40. This shape is achieved by a conventional cooling catheter as described above, where only one injection orifice or Joule-Thomson element is employed. However, this shape of cooling contour is generally not desirable when employing the catheter for cardiac mapping in addition to tissue treatment. For cardiac mapping, the catheter is first used to cool tissue so as to locate a treatment node or tissue pathway, as is well-known to those skilled in the art. The treatment node in question is shown in FIG. 40 as point “X”, or labeled as 401. For a bipolar ECG catheter, node 401 generally lies at a longitudinal point between the first ECG lead, or distal tip 405, and the second ECG lead, or ring electrode 410. To locate the node 401, the catheter 400 must be positioned and oriented relative to the node 401 as shown in FIG. 40. If cooling were initiated the catheter 400 would produce a cooling contour or iceball 424 as shown, which would not cover the treatment node 401. Thus, the catheter would need to be moved and repositioned to treat or ablate the node 401 after cryomapping such node 401.

The present invention is a device, which provides a cryotreatment catheter having an extended treatment zone or cooling contour. As used herein, the term “cryotreatment” shall mean the application of cooling to tissue of varying degrees, from minor temperature changes effecting reversible alterations in cellular structure to cryosurgical ablation and/or removal of tissue. Also as used herein, the term “tissue mapping” or “cryomapping” shall refer to the method, practice, or process of applying cooling to tissue and measuring the properties of such tissue in response to said cooling.

Turning now to FIG. 41, the present invention provides the catheter of FIG. 40, labeled generally as 400, and having, instead of a limited treatment zone 424 as shown in FIG. 40, an extended treatment zone 426 as shown in FIG. 41. The extended treatment zone is not necessarily limited to the shape or contour of zone 426, but rather may encompass any contour that is relatively larger than contour 424, extending significantly further away from the distal tip 405, so as to affect not only the tissue proximate the distal end of the catheter 400, but also the tissue along the sides of the catheter body 402.

FIG. 42 illustrates an expanded cross-sectional view of the distal end portion of the catheter 400 of FIG. 41, taken along lines A-A in FIG. 41. The distal end portion of the catheter 400 includes, in addition to distal tip 405 and first ECG ring lead 410, a fluid conduit 430 defining a return lumen 432, a first fluid injection port 435, secondary fluid injection ports 438, a distal end cap 440, one or more electrically conductive wires or leads 442, a thermally transmissive, electrically isolating catheter body section 445, a thermally conductive body section 450, and one or more seals 452. Furthermore, a longitudinal axis 455 and a transverse axis 460 are shown superimposed on the cross-section to illustrate the spatial orientation of the various elements.

As shown in FIG. 42, catheter 400 includes a fluid injection conduit 430 disposed inside of the catheter body 402 to define a fluid return lumen 432 therebetween. Coolant is supplied to conduit 430 at its proximal end (not shown) and flows along the right-facing arrows as shown in FIG. 42. The supplied coolant may be any cryogen or cryogenic fluid capable or stable operation at low temperature and high pressure, such nitrous oxide, nitrogen, AZ20, or any suitable refrigerant. The fluid exits the conduit 430 at two or more points, including a first orifice 435 at the distal end of the conduit 430, and one or more second orifices 438 defined by the lateral walls of the conduit 430, at some point less proximate the distal tip 405 than the first orifice 435. Orifice 435 may be considered a primary injection port for coolant flowing into the return lumen 432, with orifices 438 being the secondary injection ports. However, the relative flow rates of coolant flowing through the orifices may be of any combination or ratio, depending on the relative size and orientation of the orifices, which may vary considerably. In the embodiment of the present invention shown in FIG. 42, two secondary orifices 438 are disposed on opposite sides of the lateral wall of the conduit 430, such that only one opening is visible in the illustration.

The secondary orifices 438 are located anywhere along the conduit 430, further away from the distal end 405 along longitudinal axis 455. The orifices 438 may be staggered along such axis, and may have varying normal axes (not shown) that may point in any radial direction perpendicular to the longitudinal axis 455. As used herein, a “normal axis” shall mean the imaginary straight-line axis in space being perpendicular to and centered on the plane formed by the orifice, pointing in the direction of fluid flow. For example, the normal axis of the first orifice 435 is parallel and coincident with the longitudinal axis, pointing to the right in FIG. 42.

Further embodiments of the conduit 430 are illustrated in FIGS. 43A and 43B, showing two perspective views of the flow conduit of the catheter of FIG. 42. The each of FIGS. 43A and 43B, only the conduit 430 with its respective orifices 435 and 438 are shown, including the normal axes for each orifice, shown as arrows. The rest of the catheter is not illustrated for ease of reference. In FIG. 43A, the secondary orifices 438 are staggered along the longitudinal axis 455, having normal axes facing away from one another. This arrangement leads to a different shape of a freeze zone or treatment contour around the distal end portion of the catheter. FIG. 43B illustrates yet another arrangement of primary orifice 435 with the four secondary orifices. This creates yet another shape of a freeze zone or treatment contour around the distal end portion of the catheter. The present invention thus encompasses any number of arrangements of single or multiple primary and secondary orifices 435 and 438, so as to create treatment zones of a wide variety, depending on the nature of use intended for the catheter.

Referring back to FIG. 42, as fluid exits the conduit 430, it flows along the left-facing arrows of FIG. 42. The return lumen 432 may have a pressure that is significantly below the pressure in the flow conduit 430. The fluid exiting either or all of the orifices 435 and 438 may be transformed under gas expansion and evaporation to gas phase from liquid phase, thereby altering the gas dynamic and thermodynamic properties of the fluid flow. A drop in temperature may create an overall endothermic heat transfer with the environment, thereby cooling any tissue surrounding the device. To effectively transmit this cooling effect, the outer walls of the catheter 400 must be thermally “transmissive”, or readily transmit thermal heat flow. Distal end 405 may thus have a conductive end cap 440 made of a thermally conductive material such as a metal. Other suitably strong, resilient yet thermally transmissive materials may be used.

The gas dynamic expansion and evaporation discussed above is generally centered about the orifices 435 and 438. That is, mixed phase liquid/gas coolant undergoes the most rapid change in pressure and temperature directly at the locus of the orifices 435 and 438. Since end cap 440 primarily surrounds the first orifice 435, the cooling effect provided by such orifice is primarily transmitted through such cap to the surroundings. The secondary orifices 438 are separated from the primary orifice 435 along longitudinal axis 455 by a separation length “L” as shown. The portion of the catheter body immediately lateral to orifices 438 consists of catheter body section 445. Section 445 forms a portion of the outer wall of catheter 400, and completely surrounds ECG ring electrode 410. As shown in FIG. 42, ECG ring electrode 410 circumscribes the outer surface (the surface not in communication with the return lumen 432) of section 445. An electrical communication wire or lead 442 is coupled to the ring electrode.410. Section 445 is made of an electrically isolating but thermally conductive material like boron nitride, such as is manufactured by Advanced Ceramics Corporation, of Cleveland, Ohio.

Accordingly, ECG ring electrode 410 is completely isolated from the rest of the device electrically, thereby being able to function as an independent terminal for ECG sensing purposes. The wire 442 couples the electrode 410 to the electrical receiving and monitoring apparatus (not shown). It will be appreciated that the shape and configuration of both the electrode 410 and catheter body section 445 may vary widely. The only requirement is that both elements be separated from the first orifice 435 by some separation length L along the longitudinal axis. Furthermore, it is advantageous, although not entirely necessary, to have the electrode 410 disposed at a longitudinal position directly in line with the second orifices 438, such that a transverse axis parallel to the axis 460 running through orifices 438 would also run though the ring electrode 410.

Catheter body 402 also includes another section 450 adjacent to section 445. Body section 450 is also thermally conductive, but need not be electrically isolating. Both of sections 445 and 450 serve to transmit the cooling effect of fluid exiting orifices 438. A sealing element 452 may be interposed between section 450 and the rest of catheter body 402.

The net result of the cooling effect of orifice 435 and orifices 438 is to create an elongate contour 426 whereby tissue proximate the catheter is treated. This extended treatment zone covers a tissue node 401 as shown. Node 410 is longitudinally positioned at some point along separation length L, having transverse axis 460 running therethough. Separation length L may range anywhere from 1 mm to 50 mm. As shown in FIG. 42, this positional relationship may vary. Yet, the object of the invention to provide an extended treatment or freeze zone around the distal tip of catheter 400 is accomplished regardless of the particular position of treatment node 401, the example used in the drawing figures being merely one of a number of applications for which the present invention may be used.

FIG. 44 illustrates a cross-sectional view of yet another embodiment of the catheter discussed in FIGS. 41 and 42, and labeled generally as 500. Catheter 500 has a distal end portion, which includes a thermally-transmissive end cap 505 at its tip. The catheter 500 further includes a first ECG ring electrode 507 disposed between two sections of the catheter shaft 508. The catheter 500 also includes a central injection tube 510 having injection orifices 511 and 512. The tube 510 is circumscribed by the shaft 508 to define an expansion chamber 514 proximate the end cap 505 and first orifice 511, and a fluid return lumen further proximate the second orifice 512.

Cryogen is injected through the tube 510 to flow out into the expansion chamber 514 and return lumen 515, which both serve as spaces wherein the fluid is expanded and evaporated to cool the structures surrounding it. A source of vacuum may be coupled to the proximal end portion (not shown) of the catheter 500 to provide a negative pressure gradient as the expanded cryogen flows away from the tip. The flow into the return lumen 515 is shown by arrows designated as F_(in), and represents the flow rate of cryogen into the control volume CV as shown. The flow out of the control volume CV is shown by the arrows designated as F_(out), and represents the mass or volumetric flow rate of cryogen exiting the control volume CV. The control volume CV effectively covers the entire distal end portion of the catheter 500, and incorporates the locus of sources of cooling or endothermic heat flow with respect to the environment, schematically represented by the arrow Q as shown.

Varying the flow rates Fin and Fout may effect the cooling. Thus, the flow may not always be steady state, where F_(in)=F_(out). For example, in one application of the invention the flow rates may be equal, where F_(in)=F_(out) and the fluid entering the expansion chamber 514 and return lumen 515 may be just equal to the amount of fluid exiting the distal end portion or control volume CV. This would be the case of steady state flow. In another application, the initial incoming flow F_(in) would be much greater than F_(out) (F_(in)>>F_(out)), resulting in an unsteady flooding of the tip region, and creating a different cooling profile. The varying flow rates would in turn affect the time and amplitude response characteristics of heat flow Q, depending on the desired cooling profile.

Furthermore, catheter 500 includes an electrically isolating, yet thermally conductive, buffer element 525 at the distal end of the catheter shaft 508. The end cap 505 is attached not to the shaft 508 but to such element 525, thereby isolating the end cap 505 from the rest of the catheter 500. This reduces electrical or signal noise during operation of the catheter 500 as described above, such as for cryomapping.

A variety of modifications and variations of the present invention are possible in light of the above teachings. Specifically, although many embodiments are illustrated being slender and flexible, other embodiments may be thick and rigid, and introduced into the body directly through incisions or through structures such as trocars. Using nanotechnology and miniaturized valving may also control the opening and closing of the catheter openings. Furthermore, although some of the illustrated devices are particularly well suited for cardiac procedures, the same embodiments and others are equally suited to other organs and/or any body portion that would benefit from the application of thermal energy. For example, the illustrated devices may be used for treating arteries for restenosis or portions of the GI tract to stop bleeding or portions of the GU tract to treat spasm, inflammation, obstruction or malignancy. Thus, the devices as shown are not to be limited to catheters but should be viewed more broadly as cryogenic structures or portions thereof. It is therefore understood that, within the scope of the appended claims, the present invention may be practiced otherwise than as specifically described hereinabove. All references cited herein are expressly incorporated by reference in their entirety.

It will be appreciated by persons skilled in the art that the present invention is not limited to what has been particularly shown and described herein above. In addition, unless mention was made above to the contrary, it should be noted that all of the accompanying drawings are not to scale. A variety of modifications and variations are possible in light of the above teachings without departing from the scope and spirit of the invention, which is limited only by the following claims. 

1. A tissue mapping and cryotreatment catheter, comprising: an elongate catheter body having a distal tip, a fluid injection conduit disposed inside the catheter body and defining a return lumen therein, the fluid injection conduit having a distal end portion, the distal end portion defining two or more injection orifices including a first orifice and a second orifice, the first orifice being proximate the distal tip, the second orifice being longitudinally offset along the fluid injection conduit to be less proximate the distal tip than the first orifice.
 2. The catheter of claim 1, further comprising: at least one electrode disposed on the catheter body proximate the distal tip, the at least one electrode being longitudinally offset from the distal tip to be proximate the second orifice.
 3. The catheter of claim 2, wherein the distal tip is a first electrocardiogram lead and the at least one electrode is a second electrocardiogram lead.
 4. The catheter of claim 2, further comprising: a thermally transmissive and electrically insulating first body section disposed on the catheter body and longitudinally offset along the catheter body from the distal tip, the first body section surrounding the at least one electrode such that the distal tip is electrically isolated from the at least one electrode.
 5. The catheter of claim 4, wherein the first body section includes an outer surface and the at least one electrode is a circumferential ring disposed about the outer surface of the first body section of the catheter body.
 6. The catheter of claim 4, further comprising: a thermally conductive second body section disposed on the catheter body adjacent the first body section and longitudinally offset along the catheter body from the distal tip to be less proximate the distal tip than the first body section.
 7. A tissue treatment catheter, comprising: an elongate catheter body having a thermally conductive distal tip and defining a return lumen therein along a longitudinal axis, a coolant injection tube disposed in the return lumen substantially parallel to the longitudinal axis, and having a proximal end portion in fluid communication with a supply of cryogen and a distal end portion proximate the distal tip, the distal end portion defining two or more injection orifices disposed longitudinally along the distal end portion, and a thermally conductive section disposed on the catheter body proximate the distal tip.
 8. The catheter of claim 7, wherein the distal end portion of the coolant injection tube defines first, second and third orifices having first, second, and third normal axes, respectively, the first normal axis being substantially parallel to the longitudinal axis, and the second and third normal axes being substantially perpendicular to the longitudinal axis.
 9. The catheter of claim 8, wherein second and third normal axes are coincident lines in opposite direction to one another.
 10. The catheter of claim 8, wherein the distal end portion of the coolant injection tube defines a separation length along the longitudinal axis between the first orifice and the second orifice, the separation length being in a range between 1 mm and 50 mm.
 11. The catheter of claim 8, further comprising: at least one electrode disposed on the catheter body proximate the distal tip, the at least one electrode being longitudinally offset from the distal tip by the separation length.
 12. The catheter of claim 11, wherein the distal tip is a first electrocardiogram lead and the at least one electrode is a second electrocardiogram lead.
 13. The catheter of claim 11, wherein the thermally conductive section includes an outer surface and the at least one electrode is a circumferential ring disposed about the outer surface of the thermally conductive section of the catheter body.
 14. The catheter of claim 13, wherein the thermally conductive section is electrically insulating.
 15. The catheter of claim 11, further comprising: an electrically conductive wire coupled to the at least one electrode.
 16. A method of treating tissue using a catheter having distal and proximal end portions, comprising: inserting the distal end portion of a catheter into a body lumen proximate a target region of tissue, the distal end portion including a thermally conductive cap fixed to a catheter body, and a fluid injection conduit disposed inside the catheter body and defining a return lumen therein, the fluid injection conduit further defining two or more injection orifices longitudinally separated along the fluid injection conduit; supplying a flow of fluid cryogen to the proximal end portion of the catheter, the fluid injection conduit being in fluid communication with the flow of fluid cryogen; injecting the flow of fluid cryogen through the two or more injection orifices; and expanding the flow of fluid cryogen in the return lumen to cool the target tissue region.
 17. The method of claim 16, wherein the two or more injection orifices include a first orifice and a second orifice, the first orifice being proximate the thermally conductive cap, the second orifice being longitudinally offset along the fluid injection conduit to be less proximate the thermally conductive cap than the first orifice.
 18. The method of claim 18, wherein the catheter body includes at least one electrode disposed on the catheter body proximate the thermally conductive cap, the at least one electrode being longitudinally offset from the distal tip to be proximate the second orifice.
 19. The method of claim 19, further comprising: mapping a tissue node in the target region of tissue with the thermally conductive cap and the at least one electrode.
 20. The method of claim 19, further comprising: cooling the tissue node in the tissue target region after mapping the tissue node, without moving the distal end portion of the catheter.
 21. The method of claim 16, further comprising directing the flow of fluid cryogen from the return lumen away from the distal end portion of the catheter at a first flow rate, wherein the injecting of the flow of fluid cryogen through the two or more injection orifices is at a second flow rate.
 22. The method of claim 21, wherein the first and second flow rates are substantially equal.
 23. The method of claim 22, wherein the first flow rate is less than the second flow rate.
 24. A cryogenic catheter comprising: an elongated thermally-transmissive region defining a substantially longitudinal axis therethrough; a cryogenic dispensing lumen substantially traversing the elongated thermally-transmissive region, including at least one fluid outlet directing a portion of the cryogenic fluid radially towards the elongated thermally-transmissive region.
 25. The cryogenic catheter according to claim 24, wherein the cryogenic dispensing lumen further comprises a distal fluid outlet located at a distal end of the cryogenic dispensing lumen.
 26. The cryogenic catheter according to claim 24, wherein the elongated thermally-transmissive region includes a plurality of thermally-transmissive segments in spaced apart relation.
 27. The cryogenic catheter according to claim 26, further including a plurality of fluid outlets arranged in special relation with the plurality of thermally-transmissive segments.
 28. The cryogenic catheter according to claim 24, further including a electrode ring positioned at a distal end of the elongated thermally-transmissive region.
 29. A cryogenic catheter comprising: an elongated thermally-transmissive region defining a substantially longitudinal axis therethrough; and a plurality of cryogenic fluid dispensing lumens substantially traversing the elongated thermally-transmissive region and axially staggered along the longitudinal axis, wherein the plurality of cryogenic dispensing lumens include at least one fluid outlet directing a portion of cryogenic fluid away from the longitudinal axis.
 30. The cryogenic catheter according to claim 29, wherein the cryogenic fluid dispensing lumens are radially staggered about the longitudinal axis.
 31. The cryogenic catheter according to claim 29, wherein the cryogenic fluid dispensing lumens further comprise at least one distal fluid outlet located at a distal end of the cryogenic dispensing lumens. 